Mechanisms of JP-8 jet fuel cell toxicity. II. Induction of necrosis in skin fibroblasts and keratinocytes and modulation of levels of Bcl-2 family members

Inorganic polyphosphate in platelet rich plasma accelerates re-epithelialization in vitro and in vivo

Wound healing requires well-coordinated events including hemostasis, inflammation, proliferation, and remodeling. Delays in any of these stages leads to chronic wounds, infections, and hypertrophic scarring. Burn wounds are particularly problematic, and may require intervention to ensure timely progression to reduce morbidity and mortality. To accelerate burn wound healing, Platelet-Rich Plasma (PRP)¹ can be of value, since platelets release growth factor proteins and inorganic polyphosphates (polyP) that may be integral to wound healing. We used polyP-depleted keratinocyte (HaCaT) and fibroblast cell culture models to determine cell proliferation and scratch-wound repair to determine if polyP, platelet lysate, or combined treatment could accelerate wound healing. While polyP and PRP significantly reduced the open scratch-wound area in fibroblasts and keratinocytes, polyP had no effect on keratinocyte or fibroblast proliferation. PRP was also evaluated as a treatment in a murine model of full thickness wound healing in vivo, including a treatment in which PRP was supplemented with purified polyP. PRP induced significantly more rapid re-epithelialization by Day 3. Pure polyP enhanced the effects of PRP on epithelial tongues, which were significantly elongated in the PRP + high-dose polyP treatment groups compared to PRP alone. Thus, PRP and polyP may serve as an effective therapeutic combination for treating wounds.

MicroRNAs expression in ox-LDL treated HUVECs: MiR-365 modulates apoptosis and Bcl-2 expression

Endothelial cells (ECs) apoptosis induced by oxidized low-density lipoprotein (ox-LDL) is thought to play a critical role in atherosclerosis. MicroRNAs (miRNAs) are a class of noncoding RNAs that posttranscriptionally regulate the expression of genes involved in diverse cell functions, including differentiation, growth, proliferation, and apoptosis. However, whether miRNAs are associated with ox-LDL induced apoptosis and their effect on ECs is still unknown. Therefore, this study evaluated potential miRNAs and their involvement in ECs apoptosis in response to ox-LDL stimulation. Microarray and qRT-PCR analysis performed on human umbilical vein endothelial cells (HUVECs) exposed to ox-LDL identified 15 differentially expressed (4 up- and 11 down-regulated) miRNAs. Web-based query tools were utilized to predict the target genes of the differentially expressed miRNAs, and the potential target genes were classified into different function categories with the gene ontology (GO) term and KEGG pathway annotation. In particular, bioinformatics analysis suggested that anti-apoptotic protein B-cell CLL/lymphoma 2 (Bcl-2) is a target gene of miR-365, an apoptomir up-regulated by ox-LDL stimulation in HUVECs. We further showed that transfection of miR-365 inhibitor partly restored Bcl-2 expression at both mRNA and protein levels, leading to a reduction of ox-LDL-mediated apoptosis in HUVECs. Taken together, our findings indicate that miRNAs participate in ox-LDL-mediated apoptosis in HUVECs. MiR-365 potentiates ox-LDL-induced ECs apoptosis by regulating the expression of Bcl-2, suggesting potential novel therapeutic targets for atherosclerosis.

Expression Profiling of Human Epidermal Keratinocyte Response Following 1-Minute JP-8 Exposure

The cDNA microarray analysis of 9600 expressed sequence tags was performed to examine the gene expression changes in human epidermal keratinocytes after 1-minute JP-8 exposure; 151 genes were identified as JP-8 responsive and classified into 8 clusters by self organization map. Genes involved in basal transcription and translations were up-regulated, whereas genes related to DNA repair, metabolism, and keratin were mostly down-regulated. Genes encoded for growth factors, apoptosis, signal transduction, and adhesion were also altered. These results indicated that human keratinocyte responds to a single dose of JP-8 insult and revealed several cellular processes previously not associated with jet fuel exposure.

Gene expression and target tissue dose in the rat epidermis after brief JP-8 and JP-8 aromatic and aliphatic component exposures

Exposures of jet propulsion fuel 8 (JP-8) to human and laboratory animal skin have resulted in skin irritation. JP-8 is a mixture of aromatic and aliphatic hydrocarbons, which in some cases have also been shown to be irritating to the skin. In an attempt to determine if aromatic or aliphatic components could mimic the JP-8-induced gene expression response, we exposed rats to JP-8, undecane (UND), tetradecane (TET), trimethylbenzene (TMB), and dimethylnaphthalene (DMN) for 1 h and examined the epidermis to characterize the gene expression response. We also measured the concentrations of the JP-8 components in the epidermis with gas chromatography/mass spectrometry after 1-h exposures to JP-8 and pure components to determine if differences in potency could be identified. Changes in gene expression, compared to sham treatment, were studied with microarray techniques and analyzed for changes in gene ontology categories. UND and TMB exposures caused the greatest number of changes in transcript levels compared to DMN and TET. When only the specific functional and signaling pathways that were changed by JP-8 were considered, these pathways were nearly all activated by the components, but to different extents. After pure component exposures, the epidermal concentrations of the components showed no significant differences, although the differences in magnitude of either total or pathway-specific gene expression differed by a factor of 10-fold. We conclude that no single component that we studied mimicked the gene expression resulting from the JP-8 exposure but that UND had the most similar responses. These data suggest that there are differences in potency between the four components studied.

Effects of brief cutaneous JP-8 jet fuel exposures on time course of gene expression in the epidermis

The jet fuel jet propulsion fuel 8 (JP-8) has been shown to cause an inflammatory response in the skin, which is characterized histologically by erythema, edema, and hyperplasia. Studies in laboratory animal skin and cultured keratinocytes have identified a variety of changes in protein levels related to inflammation, oxidative damage, apoptosis, and cellular growth. Most of these studies have focused on prolonged exposures and subsequent effects. In an attempt to understand the earliest responses of the skin to JP-8, we have investigated changes in gene expression in the epidermis for up to 8 h after a 1-h cutaneous exposure in rats. After exposure, we separated the epidermis from the rest of the skin with a cryotome and isolated total mRNA. Gene expression was studied with microarray techniques, and changes from sham treatments were analyzed and characterized. We found consistent twofold increases in gene expression of 27 transcripts at 1, 4, and 8 h after the beginning of the 1-h exposure that were related primarily to structural proteins, cell signaling, inflammatory mediators, growth factors, and enzymes. Analysis of pathways changed showed that several signaling pathways were increased at 1 h and that the most significant changes at 8 h were in metabolic pathways, many of which were downregulated. These results confirm and expand many of the previous molecular studies with JP-8. Based on the 1-h changes in gene expression, we hypothesize that the trigger of the JP-8-induced, epidermal stress response is a physical disruption of osmotic, oxidative, and membrane stability which activates gene expression in the signaling pathways and results in the inflammatory, apoptotic, and growth responses that have been previously identified.

Underlying mechanism of hypoxic preconditioning decreasing apoptosis induced by anoxia in cultured hippocampal neurons

It is known that hypoxic preconditioning (HP, a brief period of sublethal hypoxia) provides neuroprotection against subsequent severe anoxia, but the mechanisms of this increased tolerance have not been fully elucidated. A hypoxic preconditioning model was established by exposing a 4-day hippocampal culture to 1% O(2) for 20 min/day for 8 days. The preconditioning significantly decreased the number of apoptotic neurons at reoxygenation 24 h after 4 h of severe anoxia (0% O(2)). Further study demonstrated that the degradation of mitochondrial membrane potential (MMP) was greatly inhibited and the expression of B-cell lymphoma protein-2 (Bcl-2) was increased considerably after severe anoxia in the HP groups. These results indicate that the increased anoxic tolerance, which is induced by HP in cultured hippocampal cells, may be correlated with Bcl-2 overexpression and enhanced stability of MMP, which ultimately reduces apoptosis 24 h after reoxygenation.

Effect of JP-8 jet fuel exposure on protein expression in human keratinocyte cells in culture

Dermal exposure to jet fuel is a significant occupational hazard. Previous studies have investigated its absorption and disposition in skin, and the systemic biochemical and immunotoxicological sequelae to exposure. Despite studies of JP-8 jet fuel components in murine, porcine or human keratinocyte cell cultures, proteomic analysis of JP-8 exposure has not been investigated. This study was conducted to examine the effect of JP-8 administration on the human epidermal keratinocyte (HEK) proteome. Using a two-dimensional electrophoretic approach combined with mass spectrometric-based protein identification, we analyzed protein expression in HEK exposed to 0.1% JP-8 in culture medium for 24 h. JP-8 exposure resulted in significant expression differences (p<0.02) in 35 of the 929 proteins matched and analyzed. Approximately, a third of these alterations were increased in protein expression, two-thirds declined with JP-8 exposure. Peptide mass fingerprint identification of effected proteins revealed a variety of functional implications. In general, altered proteins involved endocytotic/exocytotic mechanisms and their cytoskeletal components, cell stress, and those involved in vesicular function.

Altered Expression of γ-Synuclein and Detoxification-Related Genes in Lungs of Rats Exposed to JP-8

Many military personnel are at risk of lung damage or systemic toxicity as a result of exposure to the jet fuel JP-8. We have now used microarray analysis to characterize changes in the gene expression profile of lung tissue induced by exposure of rats to JP-8 at a concentration of 171 or 352 mg/m(3) for 1 h/d for 7 d, with the higher dose estimated to mimic the level of occupational exposure in humans. The expression of 56 genes was significantly affected by a factor of </= 0.6 or >/= 1.5 by JP-8 at the low dose. Eighty-six percent of these genes were downregulated by JP-8. The expression of 66 genes was similarly affected by JP-8 at the higher dose, with the expression of 42% of these genes being upregulated. Prominent among the latter genes was that for the centrosome-associated protein gamma-synuclein, whose expression was consistently increased. The expression of various genes related to antioxidant responses and detoxification, including those for glutathione S-transferases and cytochrome P450 proteins, were also upregulated. The microarray data were confirmed by quantitative RT-PCR analysis. Our extensive data set may thus provide important insight into the pulmonary response to occupational exposure to JP-8 in humans.

Evaluation of gene expression profile of keratinocytes in response to JP-8 jet fuel

The skin is the principal barrier against any environmental insult. Therefore, there is a high risk for a large number of military and civilian personnel exposed to jet fuel JP-8 to suffer percutaneous absorption of this fuel. This paper reports the use of cDNA microarray to identify the gene expression profile in normal human epidermal keratinocytes exposed to JP-8 for 24-h and 7-day periods. The effects of JP-8 exposure on keratinocytes at these two different periods induced a set of genes with altered expression in response to this type of insult. Microarray data were visualized using a novel algorithm based on simple statistical analyses to reduce data dimensionality and identify subsets of discriminant genes. Predictive neural networks were built using a multiplayer perceptron to carry out a proper classification task in microarray data in the untreated versus JP-8-treated samples. The pattern of expressions in response to JP-8 provides evidences that detoxificant-related and cell growth regulator genes with the most variability in the level of expression may be useful genetic markers in adverse health effects of personnel exposed to JP-8. The approaches in our analysis provide a simple, safe, novel, and effective method that is reliable in identifying and analyzing gene expression in samples treated with JP-8 or over potential toxic agents. Gene expression data from these studies can be used to build accurate predictive models that separate different molecular profiles. The data establish the use and effectiveness of these approaches for future prospective studies.

Dermal toxicity and microscopic alterations by JP-8 jet fuel components in vivo in rabbit

In this study, we investigated the skin irritation, macroscopic and microscopic barrier alteration in vivo in rabbits from aliphatic and aromatic components of jet propellant-8 (JP-8) jet fuel. Macroscopic barrier properties were evaluated by measuring transepidermal water loss (TEWL), skin capacitance, and skin temperature; microscopic changes were observed by light microscopy. Draize visual scoring system was used to measure skin irritation. We found significant (P<0.05) increase in temperature at the site of all chemically saturated patches immediately after patch removal in comparison to the control site. Tridecane (TRI) produced a greater increase in temperature and capacitance at all time points than all the other components of JP-8. Both the aliphatic and aromatic components increased the TEWL at all time points. Tridecane produced greater increase in TEWL followed by naphthalene (NAP), 1-methylnaphthalene (1-MN), 2-metylnaphthalene (2-MN), tetradecane (TET), and dodecane (DOD). All of the above components of JP-8 caused moderate to severe erythema and edema, which were not resolved to the baseline even after 24h of patch removal. Light microscopy revealed an increase in epidermal thickness (ET), and decrease in length and thickness of collagen fibers' bundle by the above components of JP-8. These results suggest potential dermatotoxicity from the JP-8 components.

Skin toxicity of jet fuels: ultrastructural studies and the effects of substance P

Topical exposure to jet fuel is a significant occupational hazard. Recent studies have focused on dermal absorption of fuel and its components, or alternatively, on the biochemical or immunotoxicological sequelae to exposure. Surprisingly, morphological and ultrastructural analyses have not been systematically conducted. Similarly, few studies have compared responses in skin to that of the primary target organ, the lung. The focus of the present investigation was 2-fold: first, to characterize the ultrastructural changes seen after topical exposure to moderate doses (335 or 67 microl/cm2) of jet fuels [Jet A, Jet Propellant (JP)-8, JP-8+100] for up to 4 days in pigs, and secondly, to determine if co-administration of substance P (SP) with JP-8 jet fuel in human epidermal keratinocyte cell cultures modulates toxicity as it does to pulmonary toxicity in laboratory animal studies. The primary change seen after exposure to all fuels was low-level inflammation accompanied by formation of lipid droplets in various skin layers, mitochondrial and nucleolar changes, cleft formation in the intercellular lipid lamellar bilayers, as well as disorganization in the stratum granulosum-stratum corneum interface. An increased number of Langerhans cells were also noted in jet fuel-treated skin. These changes suggest that the primary effect of jet fuel exposure is damage to the stratum corneum barrier. SP administration decreased the release of interleukin (IL)-8 normally seen in keratinocytes after JP-8 exposure, a response similar to that reported for SP's effect on JP-8 pulmonary toxicity. These studies provide a base upon which biochemical and immunological data collected in other model systems can be compared.

Involvement of increased stability of mitochondrial membrane potential and overexpression of Bcl-2 in enhanced anoxic tolerance induced by hypoxic preconditioning in cultured hypothalamic neurons

The effects of hypoxic preconditioning (HP) on changes in mitochondrial membrane potential (MMP) and Bcl-2 expression in cultured hypothalamic neurons after severe anoxia were investigated. In the HP group, hypothalamic neurons, after a 4-day culture, were preconditioned daily under a hypoxic condition (1% O(2), 10 min) for 8 days; subsequently, the HP neurons and those in the control group (similarly cultured, but without HP) were exposed to 6 h of severe anoxia (0% O(2)). The preconditioned neurons had a higher survival rate and a lower lactate dehydrogenase leakage, compared with the control group. Although HP did not prevent the degradation of MMP during severe hypoxia, preconditioned neurons exhibited a higher level of MMP than that of the control group. Increased expression of Bcl-2 was also observed in the preconditioned hypothalamic neurons. These results suggest that HP enhances the hypoxic tolerance of hypothalamic neurons, and the underlying mechanisms may be related to the increased stability of MMP and the overexpression of Bcl-2 induced by HP.

Macroarray analysis of the effects of JP-8 jet fuel on gene expression in Jurkat cells

The jet fuel JP-8 is widely used and a large number of military and civilian personnel is, therefore, exposed to it. Treatment of several cell lines, including human Jurkat cells, with JP-8 induces cell death that exhibits various biochemical and morphological characteristics of apoptosis. The molecular mechanism of JP-8 cytotoxicity, however, has remained unclear. The effects of exposure of Jurkat cells to JP-8 (1/10,000 dilution) for 4 h on gene expression have now been examined by cDNA macroarray analysis. We had previously shown in these cells that under the above conditions, JP-8 causes significant apoptosis, based upon the observation that caspase-3 activation occurs at approximately 4 h and consequently most of the other classical apoptotic biochemical and morphological alterations progress until apoptotic cell death at 24 h. Of the 439 apoptosis- or stress response-related genes examined, the expression of 16 genes was up-regulated and that of ten genes was down-regulated by a factor of > or =2. The changes in the expression of 11 of these 26 genes were confirmed by reverse transcription and polymerase chain reaction analysis. These results provide insight into the mechanism of JP-8 toxicity and the associated induction of apoptosis.

Biological and health effects of exposure to kerosene-based jet fuels and performance additives

Over 2 million military and civilian personnel per year (over 1 million in the United States) are occupationally exposed, respectively, to jet propulsion fuel-8 (JP-8), JP-8 +100 or JP-5, or to the civil aviation equivalents Jet A or Jet A-1. Approximately 60 billion gallon of these kerosene-based jet fuels are annually consumed worldwide (26 billion gallon in the United States), including over 5 billion gallon of JP-8 by the militaries of the United States and other NATO countries. JP-8, for example, represents the largest single chemical exposure in the U.S. military (2.53 billion gallon in 2000), while Jet A and A-1 are among the most common sources of nonmilitary occupational chemical exposure. Although more recent figures were not available, approximately 4.06 billion gallon of kerosene per se were consumed in the United States in 1990 (IARC, 1992). These exposures may occur repeatedly to raw fuel, vapor phase, aerosol phase, or fuel combustion exhaust by dermal absorption, pulmonary inhalation, or oral ingestion routes. Additionally, the public may be repeatedly exposed to lower levels of jet fuel vapor/aerosol or to fuel combustion products through atmospheric contamination, or to raw fuel constituents by contact with contaminated groundwater or soil. Kerosene-based hydrocarbon fuels are complex mixtures of up to 260+ aliphatic and aromatic hydrocarbon compounds (C(6) -C(17+); possibly 2000+ isomeric forms), including varying concentrations of potential toxicants such as benzene, n-hexane, toluene, xylenes, trimethylpentane, methoxyethanol, naphthalenes (including polycyclic aromatic hydrocarbons [PAHs], and certain other C(9)-C(12) fractions (i.e., n-propylbenzene, trimethylbenzene isomers). While hydrocarbon fuel exposures occur typically at concentrations below current permissible exposure limits (PELs) for the parent fuel or its constituent chemicals, it is unknown whether additive or synergistic interactions among hydrocarbon constituents, up to six performance additives, and other environmental exposure factors may result in unpredicted toxicity. While there is little epidemiological evidence for fuel-induced death, cancer, or other serious organic disease in fuel-exposed workers, large numbers of self-reported health complaints in this cohort appear to justify study of more subtle health consequences. A number of recently published studies reported acute or persisting biological or health effects from acute, subchronic, or chronic exposure of humans or animals to kerosene-based hydrocarbon fuels, to constituent chemicals of these fuels, or to fuel combustion products. This review provides an in-depth summary of human, animal, and in vitro studies of biological or health effects from exposure to JP-8, JP-8 +100, JP-5, Jet A, Jet A-1, or kerosene.

Percutaneous absorption, biophysical, and macroscopic barrier properties of porcine skin exposed to major components of JP-8 jet fuel

JP-8 has been associated with toxicity in animal models and humans. There is a great potential for human exposure to JP-8. Quantitation of percutaneous absorption of JP-8 is necessary for assessment of health hazards involved in its occupational exposure. In this study, we selected three aliphatic (dodecane, tridecane, and tetradecane) and two aromatic (naphthalene and 2-methylnaphthalene) chemicals, which are major components of JP-8. We investigated the changes in skin lipid and protein biophysics, and macroscopic barrier perturbation from dermal exposure of the above five chemicals. Fourier transform infrared (FTIR) spectroscopy was employed to investigate the biophysical changes in stratum corneum (SC) lipid and protein. FTIR results showed that all of the above five components of JP-8 significantly (P<0.05) extracted SC lipid and protein. Macroscopic barrier perturbation was determined by measuring the rate of transepidermal water loss (TEWL). All of the five JP-8 components studied, caused significant (P<0.05) increase in TEWL in comparison to control. We quantified the amount of chemicals absorbed assuming 0.25 m(2) body surface area exposed for 8 h. Our findings suggest that tridecane exhibits greater permeability through skin among aliphatic and naphthalene among aromatic JP-8 components. Amount of chemicals absorbed suggests that tridecane, naphthalene and its methyl derivatives should be monitored for their possible systemic toxicity.

In vivo percutaneous absorption, skin barrier perturbation, and irritation from JP-8 jet fuel components

JP-8 jet fuel has been reported to cause systemic and dermal toxicities in animal models and humans. There is a great potential for human exposure to JP-8. In this study, we determined percutaneous absorption and dermal toxicity of three components of JP-8 (i.e., xylene, heptane, and hexadecane) in vivo in weanling pigs. In vivo percutaneous absorption results suggest a greater absorption of hexadecane (0.43%) than xylene (0.17%) or heptane (0.14%) of the applied dose after 30 min exposure. Transepidermal water loss (TEWL) provides a robust method for assessing damage to the stratum corneum. Heptane showed greater increase in TEWL than the other two chemicals. No significant (p < 0.05) increase in temperature was observed at the chemically treated site than the control site. Heptane showed greater TEWL values and erythema score than other two chemicals (xylene and hexadecane). We did not observe any skin reactions or edema from these chemicals. Erythema was completely resolved after 24 h of the patch removal in case of xylene and hexadecane.

Roles of oxidative stress and glutathione depletion in JP-8 jet fuel-induced apoptosis in rat lung epithelial cells

The toxic jet fuel JP-8 induces morphological and biochemical changes characteristic of apoptosis in rat lung epithelial (RLE-6TN) cells. The mechanism of JP-8 toxicity in these cells was further investigated in an attempt to identify potential therapeutic interventions. Given that oxidative stress and changes in the concentrations of endogenous antioxidants, such as glutathione (GSH), have been associated with the cellular damage elicited by numerous toxicants, the possibility that JP-8 induces cellular oxidative stress was investigated. Experimentally induced depletion of intracellular GSH or exposure of cells to a low concentration of H(2)O(2) markedly enhanced JP-8-induced cell death. A significant reduction in intracellular concentrations of GSH was noted in RLE-6TN cells shortly after exposure to JP-8. Furthermore, JP-8 induced the generation of reactive oxygen species (ROS) in RLE-6TN cells. Consistent with the notion that JP-8 toxicity is mediated by generation of ROS and depletion of intracellular GSH, JP-8-induced cell death was inhibited by exogenous GSH or the thiol-containing antioxidant N-acetyl-cysteine. This protective effect was associated with marked inhibition of both the activation of caspase-3 and the loss of the mitochondrial membrane potential induced by JP-8. Inhibition of the JP-8-induced activation of poly(ADP-ribose) polymerase by 3-aminobenzamide did not protect cells against JP-8 toxicity. Together, these results indicate that thiol antioxidants are highly effective in rescuing cells from JP-8-induced cell death and that they may provide a basis for new therapeutic approaches to counteract JP-8 toxicity.

Detection of oxidative species and low-molecular-weight DNA in skin following dermal exposure with JP-8 jet fuel

Dermal absorption of JP-8 jet fuel can lead to skin irritation within hours after exposure. This study detected the formation of oxidative species and low-molecular-weight DNA in rat skin as potential indicators of JP-8-induced skin injury. At 0, 1, 2, 4 and 6 h after the beginning of a 1-h exposure, skin samples were removed and analyzed for oxidative species formation and low-molecular-weight DNA analysis. At 1, 2 and 4 h, mean oxidative species levels increased significantly (P < 0.05) above unexposed samples. Significantly higher (P < 0.05) low-molecular-weight DNA values were observed at 4 and 6 h compared with unexposed controls. These results demonstrate significant increases in oxidative species and low-molecular-weight DNA levels in the skin following dermal exposure to JP-8. These responses may serve as indicators of skin injury following exposure to JP-8 jet fuel and other volatile chemicals or mixtures.

Dermal toxicity: effect of jet propellant-8 fuel exposure on the biophysical, macroscopic and microscopic properties of porcine skin

The effect of jet propellant-8 (JP-8) fuel exposure on the biophysical, macroscopic and microscopic changes in vitro in porcine skin has been investigated. Fourier transform infrared (FTIR) spectroscopy was employed to investigate the biophysical changes in stratum corneum (SC) lipid and protein. FTIR results showed that the treatment of the SC with JP-8 to increasing exposure time caused correspondingly greater percent decrease in the peak heights and areas under the absorbance curve of methylene and amide absorbances, suggesting greater loss of lipid and protein from SC layers. In vitro transepidermal water loss (TEWL) studies allowed an investigation into the macroscopic barrier properties of the skin. TEWL results were in consonance with that of FTIR. There was a significant increase (P<0.05) in TEWL through 8 and 24 h JP-8 exposed skin in comparison to the control. Light microscopy provided direct, corroborative, visual evidences of epidermal and dermal alterations. Epidermal swelling, dermal matrix granulation, mast cell granules, shortened collagen fibers were observed in the skin exposed with JP-8. Thus, it is concluded that JP-8 exposure causes appreciable biophysical and histological changes along with increased TEWL values in vitro in pig skin which may lead to skin irritation and dermal toxicity in vivo.

Mechanisms of JP-8 jet fuel toxicity. I. Induction of apoptosis in rat lung epithelial cells

JP-8 is a kerosene-based fuel widely used by the U.S. military. Various models of human occupational and animal exposure to JP-8 have demonstrated the potential for local and systemic toxicity but the mechanisms involved are unknown. The purpose of our investigation was to study the molecular mechanisms of JP-8 toxicity by using an in vitro model. JP-8 exposure in a rat lung alveolar type II epithelial cell line (RLE-6TN) induces biochemical and morphological markers of apoptotic cell death: caspase-3 activation, poly(ADP-ribose) polymerase (PARP) cleavage, chromatin condensation, membrane blebbing, cytochrome c release from mitochondria, and genomic DNA cleavage into both oligonucleosomal (DNA ladder) and high-molecular-weight (HMW) fragments. The human histiocytic lymphoma cell line (U937) also responds to JP-8 with caspase-3 activation, cleavage of caspase substrates, including PARP, DNA-PK, and lamin B1, and degradation of genomic DNA with the production of HMW fragments. Caspase-3 activation and PARP cleavage also occur in the acute T-cell leukemia cell line (Jurkat) following treatment with JP-8. Furthermore, Jurkat cells stably transfected with a plasmid encoding the antiapoptotic protein Bcl-x(L) or pretreated with the pan-caspase inhibitor Boc-d-fmk, are relatively resistant to the cytotoxic effects of JP-8 compared to control cells. Finally, we demonstrate that PARP cleavage occurs in primary mouse thymocytes exposed to JP-8. In conclusion, our data support the hypothesis that apoptotic cell death is responsible at least partially for the cytotoxic effects of JP-8 and suggest that inhibition of the apoptotic cascade might reduce JP-8 toxicity.